This invention relates generally to knitting machines and, more particularly, to pattern mechanisms for circular knitting machines to provide different needle heights for patterning purposes.
Patterning in knitting machines is provided generally by controlling needle height during the time the yarn is fed to the needle hooks. Patterning effects can be provided in a number of ways, including a selection between knit and tuck, or knit and welt, and/or selection of one or more yarns fed at different heights to the needles, i.e., by raising needles selectively to two different clear heights, a needle may accept and knit only one of two yarns being fed, while another needle raised to a greater clear height may accept and knit two yarns together.
Basically, patterning is provided by various camming arrangements which serve to raise or lower the needles and their actuating mechanisms together, with an additional selecting or patterning mechanism which serves to determine whether or not a needle and its related actuating mechanism will or will not be affected by the operation of one or more of the operating cams.
With this type of patterning and the need to determine which needle will be selected for a given mode of operation and which needle will not be so selected, most systems of patterning utilize one or more pattern jacks located below the needles in the needle cylinder and operable to selectively raise the needle to one of two or more alternate heights.
In patterning systems of this kind, there has been a wide variety of arrangements utilizing, among other various arrangements, one or more pattern jacks each having from one to as many as one or two dozen or more separate spaced butts on one jack, some of which may be of different projecting lengths. However, regardless of the butt arrangements and the selector means, actual selection has generally involved movement of the entire jack, either in pivotal or other similar movement radially into or out of its slot in the needle cylinder or providing an initial vertical movement to the jack which will cause the butt to selectively miss or engage another cam to complete the selecting operation.
Although many various alternate arrangements have been proposed, one of the most important problems has been to provide and maintain accurate and dependable operation as knitting speeds are increased. To increase productivity, the obvious approach is to simply increase the rotational speed of the needle cylinder. However, increased speeds mean increased loads not only on the cams and needle butts directly involved in the knitting action but also in the jacks and butts involved in the needle selection operation. In a conventional arrangement, wherein the jack is selectively rocked into or out of its slot so that the associated butt engages or misses a selecting cam, increased rotational speeds of the needle cylinder necessitate the extremely rapid selection and movement of the jacks and, although those jacks have relatively low mass, inertia problems are difficult to overcome at the speeds involved.